烟气中NO_x的液相氧化吸收及硝态氮的去除研究

发布时间：2018-01-01 14:13

  本文关键词：烟气中NO_x的液相氧化吸收及硝态氮的去除研究　出处：《北京化工大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 氯酸盐氧化NO_x Na_2S溶液吸收NO_x NO_2~-还原

【摘要】：本文利用氧化—还原法脱硝技术,实现气相中NOx的去除,并且将被吸收进入液相的NOx利用还原剂将其还原为N2,实现NOx的无害化处理。本文首先考察了NaClO、NaClO2和ClO2等三种氯酸盐在鼓泡反应器中对NO的氧化性能,考察了氧化剂在不同氧化剂浓度、温度、pH值等条件下对NO的氧化效率；然后研究了以Na2S作为吸收剂,其溶液的浓度、温度、pH值以及NO2浓度等影响因素对N02的吸收特性,并且对该吸收反应的动力学进行了分析；最后本文对脱硝液中的N02-的处理进行了研究,采用Na2SO3还原NO2-为N2,考察了该反应在不同pH值、温度、SO32-/NO2比等对N02-去除效率的影响,同时,对尿素和铵盐法去除N02-进行研究比较。主要结论如下：实验结果表明各氧化剂在最优条件下,NaClO,和ClO2溶液对NO的氧化效率都可达到100%,NaClO对NO的氧化效率为50～60%左右,而且气相ClO2对NO的氧化效率也很高。NaClO3/NaClO和NaClO2/NaClO混合液均较单独氧化剂氧化效率强,且较经济。NaClO2/NaClO昆合液在酸性条件下产生C102,浓度比为2.5时产生的ClO2浓度最高,ClO2与混合液协同氧化使氧化效率最高。三种氧化剂都存在逃逸现象,会与后续还原剂发生反应,与吸收NO2产生竞争,消耗还原剂。三种氯酸盐反应后的产物主要以Cl-形式存在,氧化后的NO一部分转化为N02,一部分被液相吸收,转化为NO2-和NO3-,液相ClO2由于其氧化性强,将液相中被吸收的氮最终以N03-形式存在。在鼓泡反应器内研究了Na2S溶液对N02的吸收特性,研究结果表明,Na2S溶液浓度从0.30 mmol/L增加到15.8 mmol/L, NO2吸收效率和吸收速率增加明显,而且随着NO：浓度提高,NO2吸收效率增大：当Na2S浓度超过15.8 mmol/L, NO2吸收速率增加缓慢,Na2S浓度增加对吸收NO2的强化作用不再明显,同时增加NO2浓度对吸收效率影响不大,说明Na2S吸收N02的过程逐渐转为气相传质控制。气相中的02使吸收反应加速,但同时也额外消耗吸收剂。在Na2S溶液中加入NaOH、浓度达0.1%时,可强化NO2的吸收。NOx中NO含量增加会导致NOx吸收率下降；即使在有NaOH的条件下,也未观察到NOx氧化度为0.5时NO/NO2的协同吸收效应。反应为吸热反应,升高温度,吸收速率增大。增大气体流量,NO：的吸收速率也增加。Na2SO3/Na2S混合液随着Na2SO3农度增大,NO：吸收效率增大,混合液浓度增加到一定程度,吸收效率基本稳定在90%左右。被吸收NO：的一部分被还原为N2,另一部分被还原为NO2-。Na2S溶液吸收NO2的反应为关于Na2S浓度一级,NO2浓度一级的拟二级反应。Na2SO3容液还原NO2-的实验研究表明,在SO32-/NO2浓度比为3：2,溶液pH值5,温度为40℃,NO2-的去除率可达99%。与尿素和铵盐法相比,不会产生二次污染,反应条件容易控制。而且,可与烟气Na2SO3脱硝法联合,实现NOx的完全无害化处理。
[Abstract]:In this paper, the removal of NOx in gas phase is realized by oxidation-reduction method, and the NOx which is absorbed into liquid phase is reduced to N2 by reducing agent. In this paper, the oxidation performance of three chlorates, NaClO _ 2 and ClO2, to no in bubbling reactor was investigated. The oxidation efficiency of oxidizer to no was investigated under the conditions of different oxidant concentration, temperature and pH value. Then the absorption characteristics of N02 with Na2S as absorbent, solution concentration, pH value and NO2 concentration were studied, and the kinetics of the absorption reaction was analyzed. Finally, the treatment of N02- in denitrification solution was studied. The reduction of NO2- to N2- by Na2SO3 was investigated at different pH values and temperatures. The effect of SO32-/NO2 ratio on the removal efficiency of N02- at the same time. The removal of N02- by urea and ammonium salt is studied and compared. The main conclusions are as follows: the experimental results show that each oxidant is NaClO under the optimum conditions. The oxidation efficiency of no in both ClO2 solution and NaClO solution is about 50 ~ 60%. The oxidation efficiency of gaseous ClO2 to no is also very high. The oxidation efficiency of NaClO _ 3 / NaClO / NaClO2/NaClO mixture is higher than that of single oxidant. More economical. NaClO _ 2 / NaClO _ Kun solution produced C _ (102) under acidic conditions, and the highest concentration of ClO2 was obtained when the concentration ratio was 2.5. The synergistic oxidation of ClO2 and mixed solution leads to the highest oxidation efficiency. All three oxidants escape and react with the subsequent reducing agent and compete with the absorption of NO2. The products of the three chlorate reactions mainly exist in the form of Cl-. The oxidized no is partly converted to N02and partly absorbed by liquid phase and converted to NO2- and NO3-. Due to its strong oxidization, the nitrogen absorbed in liquid phase is finally in the form of N03-. The absorption characteristics of Na2S solution to N02 in bubbling reactor are studied. When the concentration of Na2S solution increased from 0. 30 mmol/L to 15. 8 mmol / L, the absorption efficiency and absorption rate of NO2 increased significantly, and with the increase of no: concentration. The absorption efficiency of NO2 increased: when the concentration of Na2S exceeded 15.8 mmol / L, the increase of NO2 absorption rate was slow. The enhancement effect of Na _ 2S concentration on the absorption of NO2 was not obvious. At the same time, increasing the concentration of NO2 has little effect on the absorption efficiency, which indicates that the absorption of N02 by Na2S is gradually controlled by gas phase mass transfer, and the absorption reaction is accelerated by O2 in gas phase. At the same time, the absorbent was also consumed. When NaOH was added to Na2S solution and the concentration reached 0.1, the increase of no content in NO2 could lead to the decrease of NOx absorptivity. Even under the condition of NaOH, the synergistic absorption effect of NO/NO2 was not observed when the oxidation degree of NOx was 0.5. The reaction was endothermic reaction, increasing temperature, increasing absorption rate and increasing gas flow rate. No: absorption rate also increased. Na2SO3 / Na2S mixture increased with the increase of Na2SO3 degree: absorption efficiency increased, and the concentration of mixed solution increased to a certain extent. The absorption efficiency is about 90%. Part of the absorbed no is reduced to N2. The other part was reduced to NO2-.Na2S solution to absorb NO2 in the first order of Na2S concentration. The experimental study of the pseudo-second-order reaction. Na2SO3 volumetric reduction of no ~-~-in the first order of NO2 concentration shows that when the concentration ratio of SO32-/NO2 is 3: 2, the pH value of the solution is 5, and the temperature is 40 鈩，

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